Por qué hay materiales que son buenos conductores?

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

What is the rate of change in a objects position?

Astone weighing 1.5 kilograms is resting on a rock at a height of 20 meters above the ground. the stone rolls down 10 meters and comes to rest on a patch of moss. the gravitational potential energy of the stone on the moss is joules.